Arc lamp



Feb. 26, 1935.

H. J. BRUNK AL ARC LAMP Filed May 7, 1932 2 Sheets-Sheet l Qt E niacin-iii!! gi /6254 K, w

Feb. 26, 1935. H. J. BRUNK ET AL ARC LAMP 2 Sheets$heet 2 Filed May 7, 195

Patented Feb. 26, 1935 UNITED STATES ARC LAMP Harold J. Brunk and Frederick F. Doerrich, Chicago, 111., assignors to The (3.. FnPease Company, a corporation of Delaware i 7 Application May 37, 1932', Serial No. 609,839

2 Claims. (01. 176-12) This invention relates to improvements in arc lamps. The main object of the invention is to provide a lamp wherein the amount of light given off is 5 much greater than what has been possible heretofore, the, improved lamp permitting the use of high amperage and at the same time eliminating certain disadvantages attendant on the use of large amounts of current.

In the use of continuous blue printing machines, for example, tracings or other negatives of difierent degrees of translucence, traveling past the bank of arc lamps, necessitate varying exposures and since commercial arc lamps now available are not adapted to vary the light emitted thereby through any considerable range, without giving rise to serious difiiculties, it has been the usual practice to change the rate of travel of the band or belt on which the sensitized papers and the tracings or other negatives travel;

In this way, the paper is exposed for a greater or less length of time as it is carried past the arc lamps. This speed variation is accompanied by the undesirable necessity of changing the drying heat where automatic printing, washing and drying is being carried out and also results in a continually fluctuating output. I. t

The present invention makes it possible to operate such machines at a constant rate; and.

. at a more rapid rate, with accompanying greatly increased output, and with a more uniform product. I I

The limitations inherent in existing arc lamps of the automatic type, wherein the carbons are fed toward each other by the mechanism, as said carbons are consumed, arise from the fact that, for various reasons, the solenoid type of operating mechanism is preferred and in such lamps,

said solenoid is connected in series with the carbons. also passes through the solenoid and, as the resistance of the arc stream is constantly changing, the current flowing through the solenoid also changes. For example, as the carbons are consumed, the arc gap lengthens, the voltage across the arc increases, the amperage decreases. the ampere turns in the solenoid decrease and hence its pull decreases also, with the result that the decreased solenoid pull permits the carbons to move closer together relatively, which, in turn, increases the current flowto'the normal value for which the lamp is set.

This operation gives good results, where a freely floating mechanism is employed and where the current which is permitted to flow is controlled The current passing through the arc within the limits for which the lamp is designed but it permits of little variation. If, for example, the solenoid is designed to operate to give a certain pull-with 3 amperes of current and it. becomes necessary to increase the amount of light radiated by the lamp to an amount represented: by a 12 ampere current,.the equilibrium is de-- stroyed if a 12 ampere current is allowed to flow, as :the pull of the coil is excessive. In addition, the increase in the number of ampere turns in the solenoid, increases the magnetic field to such an extent thatit influences the arc stream itself I in an undesirable manner. This attraction of the are by the excessive magnetic field is so great that enclosed arc lamps, consuming more than 12 amperes, have not been successful heretofore in work of this character.

In other words, it has been impracticalto vary the current consumption from the rated am-. perage; of a particular lamp except to a small degree, and, therefore, when variations in light intensity are required, as in making blue prints, blue line prints, and; the like,- the difierence must be compensated for by varying the distance betweenthe lamp and the copyor by changing the time'of exposure.

:Other objects of our invention, therefore, are to provide an enclosed arc lamp, wherein the light intensity may be varied through a Wide range; to provide means whereby the current flowing through the arc may be varied without varying the current in the solenoid; to provide an arc lamp with a variable resistance or reactance in a shunt circuit around the series coilor solenoid; to provide an arc lamp of greater stability; and to provide a bank of a considerable number of arc lamps of this character, which can be controlled as a unit and by the operation of a single dial or lever. V I Y i A further object is to provide such a lamp or bank of lamps with a switch or switches associ ated with the mechanism for raising and lowering the upper carbon, whereby the shunt circuit is automatically opened whenever the carbons are in contact with each other, thereby preventin a short'circuiti In the accompanying drawings, Fig. 1 is a perspective view of an arc lamp including its novel circuits, which will serve to illustrate the invention; i

Fig. 2 is a diagrammatic view of the same, with the carbons separated;

Fig. 3 is a circuit diagram of a bank ofarc lamps. I i e I t The are lamp shown in Fig. 1 comprises a suitable frame 10, the lower end of which has semicircular clamping members 11 whereby the lamp may be mounted on a tubular support. A horizontal platform or shelf 12 is carried on said frame 10 and a pair of vertical rods 13 extend upwardly from said shelf and serve as guides for a vertically slidable cross head of insulating material 14, such, for example, as porcelain. This cross head carries a socket member 15 in which the upper carbon 16 is clamped. The

lower carbon 17 is suitably carried by a supporting bracket 18 when the lamp is not operating, the upper carbon rests on the lower carbon as shown in this perspective view. The carbons are preferably surrounded by the usual globe 19. The mounting for said globe forms no part of the present invention but the same may be constructed as shown in the patent of Harold J. Brunk, 1,867,305, which issued July 12, 1932, based on an application Serial No. 421,091, filed January 16, 1930.

When the lamp is connected in circuit, the upper'carbon is raisedby a suitable clutch mechanism, actuated by a solenoid 20 and its slotted core 21. In this instance, the core is fixed to the base 12 and the solenoid moves, but the rel ative arrangement may be reversed, as is well understood. Said solenoid is supported by depending links 22, carried by a U shaped frame 23, which is pivoted at 24 to the upright members 13 whereby said frame may rock up and down. A suitable adjustable link 25 is fastened to the end of the frame opposite the solenoid and carries at its lower end a clutch 26 pivotally supported at 27 and arranged to engage the upper carbon 16 and raise the same when the solenoid is enersized, and thus draws itself down about its fixed core. The weight of the solenoid is balanced by a counter-weight 28, and a suitable dashpot 29 checks the movement of the solenoid, clutch and associated parts.

The supply circuit 3030 may be assumed to represent a 220 volt A. C. line, although the lamp may be made to operate also on volt supply circuit or on a D. C. circuit. The local circuit to the lamp includes conductors 31, 31 and a reactoror a resistance 32, the conductors terminating at the binding post 33. A resistance is used where the source of supply is direct current and a reactor is used for alternating current. The'circuit from the binding post 33 is through the solenoid 20 and back to the binding post 34 and thence through flexible conductor 35 to the upper terminal 15 in which the movable carbon is clamped.

In order to permit greater flow of current through the are when the lamp is in operation and increase the light emitted thereby without materially increasing the magnetic effect of the solenoid, we provide a shunt circuit around the latter, as indicated by conductor 36, variable resistance or reactor 37 and conductor 38. A circuit interrupter 39, which is preferably in the form of a mercury switch which may be included in said shunt circuit, and is shown mounted in a suitable housing 40 on a pivoted Ushaped frame 23. A conductor 41 completes the shunt circuit from said switch to the binding post 34 and hence completes the circuit to the upper carbon. When the mercoid switch is in the position shown in Fig. 1, the carbons are in contact with each other and the frame 23 is tilted in such a direction that the shunt circuit around the solenoid is opened at said mercoid switch; thus a short circuit around said solenoid and through said carbons is prevented. When the solenoid is energized, it moves downwardly, thereby raising the clutch and lifting the upper carbon to strike an arc, and at the same time said mercury switch is tilted to the position shown in Fig. 2, in which the shunt circuit around said solenoid is closed. However, when the circuit to the lamp as a whole is closed, the carbons are separated so quickly that the short circuit is broken almost instantly and under most conditions no difficulty arises and therefore the switch in said shunt circuit may be omitted.

The solenoid is designed with the minimum number of ampere turns required to separate the carbons with the balanced mechanism described and at the smallest amperage which will start or maintain an are on the particular voltage used. For example, on a 220 volt circuit, 4 amperes through the solenoid may be considered the minimum under many conditions, although, due to the eifect of the shunt circuit hereinafter described, the lamp may operate on a wide range of current, for example up to possibly 45 amperes, as measured at the terminals, although, for commercial purposes, a range of 8 amperes to 25 amperes may be considered as suitable limits, for an enclosed arc type of lamp. For an open arc type the range may be very much higher. The current flowing through the solenoid, with either type of lamp, is, as stated, comparatively small, varying from 4 to 6 or 8 amperes. The relatively small magnetic field, resulting from the above mentioned low amperage coil, will not materially affect the arc.

With the lamp shown, the reactor 32 may be assumed to be a 7% ampere fixed reactor and the reactor 37 in the shunt circuit may be assumed to be a 10 to 28 ampere variable reactor. With this arrangement, the are between the carbons may be fed not only by the small current flowing through the solenoid but by the additional current flowing through the shunt circuit, including the variable reactance. The current through the are, as previously stated, may be caused to run as high as 45 amperes, or even higher, depending upon the adjustment of the variable reactance. This adjustment may be readily made by hand, decreasing the resistance of the shunt circuit to increase the current flowing through it and hence through the arc, whereby the light emitted by the arc may be increased, i. e. may be varied throughout a wide range and, particularly, the actinic rays may be increased in a much greater ratio than the increase in amperage. For example, if the current flowing through the arc is increased from 12 amperes to 24 amperes, the effective light for photographic purposes which emanates from the lamp is increased, not twice but about three times. It will thus be seen that where the lamp is used as part Of a bank of lamps in a blue print machine, the speed of printing may be greatly increased, and when it is necessary to vary the light, this is done merely by adjusting the variable reactor by hand while the machine is operating.

With this improved lamp, greater stability is obtained, as the solenoid current is held substantially constant by the highly conducting vapor path formed by the arc, as a result of the additional current flowing in the shunt side of the circuit, and also on alternating current, where the reactance is used, a phase difference exists between the two reactors operating in different circuits and set at varying current values. This phase difference manifests itself in slightly overlapping curves representing the cycles, the effect of which is to increase the heat and therefore increase the stability of the arc stream. In View of the greatly intensified arc, the relatively small magnetic field, resulting from the solenoid, has little effect thereon.

Fig. 3 illustrates a battery of arc lamps, which, although shown diagrammatically, may be assumed to be similar to those shown in Fig. 1, the same reference characters being applied to certain parts to indicate those corresponding to what has previously been described. The variable reactances 37A, 37B, 37C, 37D and 37E may each be controlled by a sliding or swinging contact arm 42A, 42B, 42C, 42D, and 42E, said arms being mounted on a single shaft 43 and rotated by a hand wheel 44, or a dial, whereby the operator may readily vary the light emitted by all of the lamps simultaneously.

The lamps described herein are of the enclosed arc type particularly adapted for use with so-called continuous blue printing machines such as illustrated, for example, in an application Serial No. 536,378, filed May 11, 1931, by the same applicant and issued May 31, 1932, to the same assignee, as Patent 1,861,298. They are not, however, limited to such use but are obviously adapted to a wide range of service. Also, the improved shunt circuit connection is effective with the open flame arc type lamp as will be evident.

We claim as our invention:

1. A bank of separate arc lamps connected in parallel each comprising a pair of relatively movable carbons, a solenoid in series with each pair of carbons for causing said relative movement, a shunt circuit normally closed around each solenoid, whenever current is flowing through the same, a current regulating device in each of said shunt circuits and means for simultaneously actuating all of said devices.

2. In combination, a group of arc lamps connected in parallel to a supply circuit, each lamp having a circuit comprising a pair of relatively movable carbons between which the are forms, a solenoid in series with each lamp, a shunt circuit around said solenoid to one of said carbons, to augment the current flowing in said are whenever the same is established, without increasing the current flowing in said solenoid, and a current regulating device in said shunt circuit.

HAROLD J. BRUNK. FREDERICK F. DOERRICH. 

